1. Field of the Invention
This invention relates to photographic materials, their preparation and their use. In particular, this invention relates to the preparation and use of latex copolymers of the acrylic type to improve the physical properties of photographic layers containing hydrophilic colloids. The copolymers disclosed herein impart added stability to photographic emulsions and cause desirable increased photographic speed and improved contrast, as well as dye hue shifts in color reversal-type photographic materials.
2. Description of the Prior Art
Proteinaceous hydrophilic colloids are known to be useful in many connections, particularly those of a photographic nature, due to the optical clarity of attenuated products which may be prepared therefrom. Gelatin or gelatin derivatives, for example, are typical of the hydrophilic colloids which have been found to be useful in this respect.
However, their colloids exhibit physical properties which are objectionable in certain applications. Many of these objections have been met by mixing or "extending" the colloid with one or more synthetic materials such as synthetic polymers. Exemplary of the art showing the use of polymers with colloids such as gelatin to overcome various problems are U.S. Pat. No. 3,411,911 (Dykstra), issued Nov. 19, 1968; U.S. Pat. No. 3,536,491 (Rees et al), issued Oct. 27, 1970; U.S. Pat. No. 3,628,957 (Franco et al), issued Dec. 21, 1971; U.S. Pat. No. 3,700,456 (Smith), issued Oct. 24, 1972; U.S. Pat. No. 3,745,007 (Nagae et al), issued July 10, 1973; U.S. Pat. No. 3,811,897 (Babbit et al), issued May 21, 1974; British Specification No. 1,147,139, published Apr. 2, 1969; British Specification No. 1,178,177, published Jan. 21, 1970; and British Specification No. 1,351,767, published May 1, 1974.
In particular, U.S. Pat. Nos. 2,739,137 (Fowler), issued Mar. 20, 1956; 2,772,163 (Tong), issued Nov. 27, 1956; and 2,852,386 (Tong), issued Sept. 16, 1958 disclose the preparation of hydrosols comprising copolymers of unsaturated aliphatic amides, acrylic acid esters and a styrene compound and their use in photographic emulsions to disperse color couplers and to improve the flexibility of gelatin and like colloids. British Pat. No. 1,181,508, published Feb. 18, 1970 and its addition, published Feb. 18, 1970 relates to a gelatin extender which is a copolymer comprising two acrylic acid esters, one of which has an active methylene group in an alcohol moiety of the ester or a substituent and a sulfoester monomer. The copolymers can be crosslinked through the active methylene groups to provide stability to the gelatin binder. These polymers, however, have been shown to be susceptible to the formation of microscopic and macroscopic agglomerates when treated with water-miscible solvents or water-soluble salts. The compositions of the present invention have unexpectedly overcome these stability problems.
Sulfoester monomers have been copolymerized with other ethylenically unsaturated monomers for various purposes. Particularly, acrylamidosulfonates have been homopolymerized and copolymerized with acrylonitriles for use as water-soluble films and as textile fibers, as disclosed in U.S. Pat. Nos. 2,983,712 (Wilkinson), issued May 9, 1961; 3,332,904 (La Combe et al), issued July 25, 1967; and 3,506,707 (Miller et al), issued Apr. 14, 1970. U.S. Pat. No. 3,547,899 (Arlt et al), issued Dec. 15, 1970 and British Specification No. 1,197,323, published July 1, 1970 disclose the copolymerization of acrylamidosulfonates with a variety of monomers, including alkyl esters and styrene to prepare copolymers useful as films and fibers showing a high degree of whiteness and an outstanding affinity for basic dyes. These references teach no photographic uses for these polymers.
Many latex polymers which are used as gelatin extenders, particularly those disclosed by U.S. Pat. Nos. 2,739,137 (Fowler); 2,772,163 (Tong); and 2,852,386 (Tong), are susceptible to gelatin-latex agglomeration and coagulation caused by salts and organic solvents. This agglomeration in coating melts leads to limited melt stability, excessive filter plugging and coating defects commonly referred to as "double-ended comets." Further, due to this agglomeration, partially-used melts cannot be sent to storage for reuse at a later time. The result is considerable waste and less than optimum flexibility in preparing melts and scheduling emulsion coating machines.
Hence, there is a continuing search for latex polymers which can be used as gelatin extenders which are not susceptible to the problems disclosed hereinabove. These polymers must be stable to organic solvents and dissolved salts normally used in photographic emulsions.